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Interface Segregation Principle

No code should be forced to depend on methods it does not use. 1

Robert C. Martin

This principle discusses that when you have an static language like Java or C#, each of the application that needs to implement an interface it needs to implement all the methods, even the ones that they don't use.

This principles proposes that instead of having a large interface that implements all the methods, it creates sub interfaces that each implement the methods that are required by the class.

This is not a problem on dynamic languages like python or ruby because this checks happens at runtime instead of compile time.

ISP is a language issue, rather than an architecture issue

There is an exception, Go is a compiled language that support this interface behavior like dynamic languages because go doesn't implement the interfaces but rather if uses Duck Typing at compile time to check if the methods that are required are implement without the need to import them.

  1. Robert C. Martin. Agile Software Development: Principles, Patterns, and Practices, Pearson Education, 2002.↩